<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>后盾人</title>
  </head>
  <body></body>
  <script>
    //\w \d
    // let hd = "houdunren2010_@@";
    // console.log(hd.match(/\w+/));
    // let email = "&^&**(*&*^2300071698@qq.com";
    // console.log(email.match(/^\w+@\w+\.\w+$/));
    //\W
    // console.log("hdcms@".match(/\W/));
    // a  \w   5 10
    let username = prompt("请输入用户名");
    // 8houdunren
    console.log(/^[a-z]\w{4,9}$/.test(username));
  </script>
</html>
